JP6756317B2 - Internal combustion engine exhaust system - Google Patents

Internal combustion engine exhaust system Download PDF

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JP6756317B2
JP6756317B2 JP2017165572A JP2017165572A JP6756317B2 JP 6756317 B2 JP6756317 B2 JP 6756317B2 JP 2017165572 A JP2017165572 A JP 2017165572A JP 2017165572 A JP2017165572 A JP 2017165572A JP 6756317 B2 JP6756317 B2 JP 6756317B2
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fuel ratio
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internal combustion
combustion engine
exhaust
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JP2019044611A (en
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剛 林下
剛 林下
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Toyota Motor Corp
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/14—Introducing closed-loop corrections
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/14—Introducing closed-loop corrections
    • F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
    • F02D41/1444—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases
    • F02D41/1454—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases the characteristics being an oxygen content or concentration or the air-fuel ratio
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/14—Introducing closed-loop corrections
    • F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
    • F02D41/1477—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the regulation circuit or part of it,(e.g. comparator, PI regulator, output)
    • F02D41/1479—Using a comparator with variable reference
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M15/00—Testing of engines
    • G01M15/04—Testing internal-combustion engines
    • G01M15/10—Testing internal-combustion engines by monitoring exhaust gases or combustion flame
    • G01M15/102—Testing internal-combustion engines by monitoring exhaust gases or combustion flame by monitoring exhaust gases
    • G01M15/104—Testing internal-combustion engines by monitoring exhaust gases or combustion flame by monitoring exhaust gases using oxygen or lambda-sensors
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/416—Systems
    • G01N27/417—Systems using cells, i.e. more than one cell and probes with solid electrolytes
    • G01N27/4175—Calibrating or checking the analyser
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/14—Introducing closed-loop corrections
    • F02D41/1401—Introducing closed-loop corrections characterised by the control or regulation method
    • F02D2041/1413—Controller structures or design
    • F02D2041/1431—Controller structures or design the system including an input-output delay
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/14—Introducing closed-loop corrections
    • F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
    • F02D41/1444—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases
    • F02D2041/147—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases the characteristics being a hydrogen content or concentration of the exhaust gases
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/24—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means
    • F02D41/26—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means using computer, e.g. microprocessor
    • F02D41/28—Interface circuits
    • F02D2041/281—Interface circuits between sensors and control unit
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/24—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means
    • F02D41/2406—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means using essentially read only memories
    • F02D41/2425—Particular ways of programming the data
    • F02D41/2429—Methods of calibrating or learning
    • F02D41/2451—Methods of calibrating or learning characterised by what is learned or calibrated
    • F02D41/2474—Characteristics of sensors

Description

本発明は、内燃機関の排気装置に関する。 The present invention relates to an exhaust device for an internal combustion engine.

内燃機関の排気中に含まれるＣＯやＨＣと水（Ｈ２Ｏ）とが反応して水素（Ｈ２）が発生することがある。この水素の影響を酸素センサが受けて、酸素センサによって検出される空燃比（以下、検出空燃比ともいう。）が実際の空燃比（以下、実空燃比ともいう。）からずれてしまうことが知られている。これに対して、排気の水素濃度に基づいて検出空燃比やセンサ出力の応答性を補正する技術が知られている（例えば、特許文献１−３参照。）。 CO and HC contained in the exhaust gas of an internal combustion engine may react with water (H 2 O) to generate hydrogen (H 2 ). The oxygen sensor is affected by this hydrogen, and the air-fuel ratio detected by the oxygen sensor (hereinafter, also referred to as the detected air-fuel ratio) may deviate from the actual air-fuel ratio (hereinafter, also referred to as the actual air-fuel ratio). Are known. On the other hand, a technique for correcting the detected air-fuel ratio and the responsiveness of the sensor output based on the hydrogen concentration of the exhaust gas is known (see, for example, Patent Documents 1-3).

特開２０００−００８９２０号公報Japanese Unexamined Patent Publication No. 2000-008920 特開２０１１−２４７０９３号公報Japanese Unexamined Patent Publication No. 2011-247093 特開２０１３−１８５５１２号公報Japanese Unexamined Patent Publication No. 2013-185512

しかし、排気の水素濃度に基づいて検出空燃比を補正しても、なお、水素の影響で検出空燃比が実空燃比からずれる場合がある。すなわち、排気の水素濃度を正確に求め、この水素濃度に基づいて検出空燃比を補正したとしても、水素の影響による検出空燃比と実空燃比とのずれを無くすことは困難であった。 However, even if the detected air-fuel ratio is corrected based on the hydrogen concentration of the exhaust gas, the detected air-fuel ratio may still deviate from the actual air-fuel ratio due to the influence of hydrogen. That is, even if the hydrogen concentration of the exhaust gas is accurately obtained and the detected air-fuel ratio is corrected based on this hydrogen concentration, it is difficult to eliminate the difference between the detected air-fuel ratio and the actual air-fuel ratio due to the influence of hydrogen.

本発明は、上記したような問題点に鑑みてなされたものであり、その目的は、水素により酸素センサの検出値が実際の値からずれることによる影響を軽減することにある。 The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to reduce the influence of hydrogen deviating from the actual value detected by the oxygen sensor.

本発明の態様の一つは、内燃機関の排気通路に設けられ拡散律速層を有し排気の空燃比を検出する酸素センサと、前記酸素センサの検出値を補正する制御装置であって、内燃機関の運転状態が同じ状態の下では、前記内燃機関の空燃比が変化したときの前記酸素センサの応答性が、高いときは低いときよりも、前記酸素センサの検出値の補正量を空燃比が大きくなる側により大きくする制御装置と、を備える内燃機関の排気装置である。 One aspect of the present invention is an oxygen sensor provided in an exhaust passage of an internal combustion engine and having a diffusion rate-determining layer to detect the air-fuel ratio of exhaust gas, and a control device for correcting the detection value of the oxygen sensor. Under the same operating state of the engine, when the response of the oxygen sensor when the air-fuel ratio of the internal combustion engine changes is high, the correction amount of the detected value of the oxygen sensor is adjusted to the air-fuel ratio. It is an exhaust device of an internal combustion engine including a control device for increasing the size on the side where the value increases.

酸素センサは、実空燃比が同一であっても排気の水素濃度によって検出空燃比が変化する。ここで、酸素センサは、酸素センサの応答性によって水素の影響の受けやすさが変化することが新たに見出された。酸素センサの応答性は、実際の空燃比が変化してから、酸素センサの検出値がどの程度の速さで変化するのかを示す値である。水素は、排気中に含まれる酸素等の他の分子に比べて分子量が小さいため、酸素センサが有する拡散律速層における拡散速度が速く、拡散律速層を通過しやすい。そうすると、排気が拡散律速層を通過する際の水素の減少量が、他の分子の減少量と比較して少なくなる。このため、排気が拡散律速層を通過すると、他の分子の濃度に対する水素濃度が相対的に高くなる。酸素センサの応答性が高い場合には、水素が拡散律速層をより通過し易くなる。そのため、酸素センサの応答性が高いときは低いときよりも、水素の影響を受け易くなり、検出空燃比がより小さい側にずれる。したがって、内燃機関の運転状態が同じ状態の下では、酸素センサの応答性が、高いときは低いときよりも、酸素センサの検出値の補正量を空燃比が大きくなる側により大きくすることにより、検出空燃比を実空燃比に近付けることができる。
これにより、水素による酸素センサの検出値と実際の値とのずれの影響を軽減することができる。 Even if the actual air-fuel ratio of the oxygen sensor is the same, the detected air-fuel ratio changes depending on the hydrogen concentration in the exhaust gas. Here, it was newly found that the susceptibility of the oxygen sensor to the influence of hydrogen changes depending on the responsiveness of the oxygen sensor. The responsiveness of the oxygen sensor is a value indicating how quickly the detected value of the oxygen sensor changes after the actual air-fuel ratio changes. Since hydrogen has a smaller molecular weight than other molecules such as oxygen contained in the exhaust, the diffusion rate in the diffusion rate-determining layer of the oxygen sensor is high, and hydrogen easily passes through the diffusion rate-determining layer. Then, the amount of decrease in hydrogen when the exhaust gas passes through the diffusion-controlled layer is smaller than the amount of decrease in other molecules. Therefore, when the exhaust gas passes through the diffusion-controlled layer, the hydrogen concentration becomes relatively high with respect to the concentration of other molecules. When the responsiveness of the oxygen sensor is high, hydrogen is more likely to pass through the diffusion-controlled layer. Therefore, when the responsiveness of the oxygen sensor is high, it is more susceptible to hydrogen than when it is low, and the detected air-fuel ratio shifts to the smaller side. Therefore, under the same operating condition of the internal combustion engine, when the responsiveness of the oxygen sensor is high, the correction amount of the detected value of the oxygen sensor is made larger on the side where the air-fuel ratio is larger than when it is low. The detected air-fuel ratio can be brought closer to the actual air-fuel ratio.
This makes it possible to reduce the influence of the deviation between the detected value of the oxygen sensor and the actual value due to hydrogen.

また、本発明の態様の一つは、内燃機関の排気通路に設けられ拡散律速層を有し排気の空燃比を検出する酸素センサと、前記酸素センサにより検出される空燃比と、比較対象となる空燃比と、を比較した結果に基づいて所定の処理を行う処理装置と、前記比較対象となる空燃比を補正する制御装置であって、内燃機関の運転状態が同じ状態の下では、前記内燃機関の空燃比が変化したときの前記酸素センサの応答性が、高いときは低いときよりも、前記比較対象となる空燃比の補正量を空燃比が小さくなる側により大きくする制御装置と、を備える内燃機関の排気装置である。 Further, one aspect of the present invention is an oxygen sensor provided in an exhaust passage of an internal combustion engine and having a diffusion rate-determining layer to detect the air-fuel ratio of exhaust, and an air-fuel ratio detected by the oxygen sensor, and a comparison target. A processing device that performs a predetermined process based on the result of comparison with the air-fuel ratio, and a control device that corrects the air-fuel ratio to be compared, and the operation state of the internal combustion engine is the same. When the responsiveness of the oxygen sensor when the air-fuel ratio of the internal combustion engine changes is high, the correction amount of the air-fuel ratio to be compared is made larger on the side where the air-fuel ratio becomes smaller than when it is low. It is an exhaust device of an internal combustion engine provided with.

検出空燃比を用いた所定の処理を行う場合には、検出空燃比を補正する代わりに、検出空燃比の比較対象となる空燃比を補正することによっても、酸素センサの水素による影響を軽減することができる。所定の処理には、例えば、検出空燃比が目標空燃比に近付くようなフィードバック制御、検出空燃比と閾値とを比較することにより行う装置の異常診断、などを挙げることができる。この場合、目標空燃比や閾値が「比較対象となる空燃比」である。 When performing a predetermined process using the detected air-fuel ratio, instead of correcting the detected air-fuel ratio, the effect of hydrogen on the oxygen sensor is also reduced by correcting the air-fuel ratio to be compared with the detected air-fuel ratio. be able to. Predetermined processing includes, for example, feedback control so that the detected air-fuel ratio approaches the target air-fuel ratio, abnormality diagnosis of the device performed by comparing the detected air-fuel ratio with the threshold value, and the like. In this case, the target air-fuel ratio or threshold value is the "air-fuel ratio to be compared".

また、前記制御装置は、排気の水素濃度が高いときは低いときよりも、補正量を大きくすることができる。 Further, the control device can make the correction amount larger when the hydrogen concentration in the exhaust gas is high than when it is low.

排気の水素濃度が高いほど酸素センサの検出値のずれが大きくなるため、これに合わせて酸素センサにより検出される空燃比、または比較対象となる空燃比を補正することにより、水素による酸素センサの検出値のずれの影響を軽減することができる。 The higher the hydrogen concentration in the exhaust gas, the larger the deviation of the detected value of the oxygen sensor. Therefore, by correcting the air-fuel ratio detected by the oxygen sensor or the air-fuel ratio to be compared, the oxygen sensor using hydrogen can be adjusted accordingly. The effect of deviation of the detected value can be reduced.

また、前記制御装置は、前記内燃機関の負荷が高いときは低いときよりも、補正量を大きくすることができる。 Further, the control device can make the correction amount larger when the load of the internal combustion engine is high than when it is low.

排気の水素濃度は内燃機関の負荷と相関があり、内燃機関の負荷が高いほど排気の水素濃度が高くなる。したがって、内燃機関の負荷に基づいた補正を行うことにより、水素による酸素センサの検出値のずれの影響を軽減することができる。なお、内燃機関の負荷は、内燃機関の吸入空気量及び空燃比と相関があるため、内燃機関の吸入空気量及び空燃比に基づいて補正量を調整することもできる。 The hydrogen concentration in the exhaust has a correlation with the load on the internal combustion engine, and the higher the load on the internal combustion engine, the higher the hydrogen concentration in the exhaust. Therefore, by performing the correction based on the load of the internal combustion engine, it is possible to reduce the influence of the deviation of the detection value of the oxygen sensor due to hydrogen. Since the load of the internal combustion engine correlates with the intake air amount and the air-fuel ratio of the internal combustion engine, the correction amount can be adjusted based on the intake air amount and the air-fuel ratio of the internal combustion engine.

また、前記制御装置は、前記内燃機関の排気の温度が低いときには高いときよりも、補正量を大きくすることができる。 Further, the control device can make the correction amount larger when the temperature of the exhaust gas of the internal combustion engine is low than when it is high.

排気の水素濃度は内燃機関の排気の温度と相関があり、排気の温度が低いほど排気の水素濃度が高くなる。したがって、内燃機関の排気の温度に基づいた補正を行うことにより、水素による酸素センサの検出値のずれの影響を軽減することができる。なお、排気の温度が所定温度以上の場合には、排気中にほとんど水素が存在しないので、補正量を０としてもよい。 The hydrogen concentration in the exhaust has a correlation with the temperature of the exhaust of the internal combustion engine, and the lower the exhaust temperature, the higher the hydrogen concentration in the exhaust. Therefore, by performing the correction based on the temperature of the exhaust gas of the internal combustion engine, it is possible to reduce the influence of the deviation of the detection value of the oxygen sensor due to hydrogen. When the exhaust temperature is equal to or higher than the predetermined temperature, almost no hydrogen is present in the exhaust, so the correction amount may be set to 0.

本発明によれば、水素により酸素センサの検出値が実際の値からずれることによる影響を軽減することができる。 According to the present invention, it is possible to reduce the influence of hydrogen causing the detection value of the oxygen sensor to deviate from the actual value.

実施形態に係る内燃機関と、その吸気系および排気系と、の概略構成を示す図である。It is a figure which shows the schematic structure of the internal combustion engine which concerns on embodiment, and its intake system and exhaust system. 空燃比センサの検出素子主要部の断面構造を示した図である。It is a figure which showed the cross-sectional structure of the detection element main part of an air-fuel ratio sensor. 実際の排気の水素濃度と空燃比センサの検出空燃比のずれ量（検出空燃比ずれ量）との関係を示した図である。It is a figure which showed the relationship between the hydrogen concentration of the actual exhaust gas and the deviation amount (the detection air-fuel ratio deviation amount) of the detection air-fuel ratio of an air-fuel ratio sensor. 実際の排気の水素濃度と空燃比センサの検出空燃比のずれ量（検出空燃比ずれ量）との関係を空燃比センサの応答性毎に示した図である。It is a figure which showed the relationship between the hydrogen concentration of the actual exhaust gas and the deviation amount (detection air-fuel ratio deviation amount) of the detected air-fuel ratio of an air-fuel ratio sensor for each responsiveness of an air-fuel ratio sensor. 応答性と水素濃度と検出空燃比ずれ量との関係を示した図である。It is a figure which showed the relationship between the responsiveness, the hydrogen concentration, and the detected air-fuel ratio deviation amount. 検出空燃比を補正するときの各種値の推移を示したタイムチャートである。It is a time chart which showed the transition of various values when correcting the detected air-fuel ratio. 係数ＲＥを求めるためのフローチャートである。It is a flowchart for obtaining a coefficient RE. 検出空燃比の補正を行うフローを示したフローチャートである。It is a flowchart which showed the flow which performs the correction of the detected air-fuel ratio. 目標空燃比の補正を行うフローを示したフローチャートである。It is a flowchart which showed the flow which performs the correction of a target air-fuel ratio. 目標となる空気過剰率λを排気の水素濃度及び検出空燃比の時定数毎に示した図である。It is a figure which showed the target air excess ratio λ for each time constant of the hydrogen concentration of exhaust and the detected air-fuel ratio.

以下に図面を参照して、本発明を実施するための形態を説明する。ただし、この実施形態に記載されている構成部品の寸法、材質、形状、その相対配置などは、特に記載がない限りは、この発明の範囲をそれらのみに限定する趣旨のものではない。 Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. However, unless otherwise specified, the dimensions, materials, shapes, relative arrangements, etc. of the components described in this embodiment are not intended to limit the scope of the present invention to those.

（実施形態）
図１は、本実施形態に係る内燃機関１と、その吸気系および排気系と、の概略構成を示す図である。内燃機関１は車両駆動用の内燃機関である。ただし、内燃機関１はディーゼルエンジンであってもよく、ガソリンエンジンであってもよい。内燃機関１には排気通路２が接続されている。排気通路２には、触媒３が設けられている。なお、実施形態において触媒３は必須の構成ではない。 (Embodiment)
FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine 1 according to the present embodiment and its intake system and exhaust system. The internal combustion engine 1 is an internal combustion engine for driving a vehicle. However, the internal combustion engine 1 may be a diesel engine or a gasoline engine. An exhaust passage 2 is connected to the internal combustion engine 1. A catalyst 3 is provided in the exhaust passage 2. The catalyst 3 is not an essential configuration in the embodiment.

さらに、触媒３よりも上流の排気通路２には、触媒３に流れ込む排気の空燃比を検出する空燃比センサ１１と、触媒３に流れ込む排気の温度を検出する温度センサ１２と、が設けられている。また、内燃機関１には各気筒に夫々燃料を噴射する燃料噴射弁６が設けられている。この空燃比センサ１１は、例えば限界電流式の酸素センサであり、広い空燃比領域に亘って空燃比に略比例した出力を発生させる。なお、空燃比センサ１１は、限界電流式の酸素センサに限らず、例えば起電力式（濃淡電池式）の酸素センサであってもよい。なお、本実施形態においては、空燃比センサ１１が、本発明における酸素センサに相当する。 Further, an air-fuel ratio sensor 11 for detecting the air-fuel ratio of the exhaust gas flowing into the catalyst 3 and a temperature sensor 12 for detecting the temperature of the exhaust gas flowing into the catalyst 3 are provided in the exhaust passage 2 upstream of the catalyst 3. There is. Further, the internal combustion engine 1 is provided with a fuel injection valve 6 for injecting fuel into each cylinder. The air-fuel ratio sensor 11 is, for example, a limit current type oxygen sensor, and generates an output substantially proportional to the air-fuel ratio over a wide air-fuel ratio region. The air-fuel ratio sensor 11 is not limited to the limit current type oxygen sensor, and may be, for example, an electromotive force type (concentration cell type) oxygen sensor. In the present embodiment, the air-fuel ratio sensor 11 corresponds to the oxygen sensor in the present invention.

また、内燃機関１には、吸気通路７が接続されている。吸気通路７には、内燃機関１の吸入空気量を検出するエアフローメータ２３が取り付けられている。 Further, an intake passage 7 is connected to the internal combustion engine 1. An air flow meter 23 for detecting the amount of intake air of the internal combustion engine 1 is attached to the intake passage 7.

そして、内燃機関１には制御装置（コントローラ）として、電子制御ユニットであるＥＣＵ１０が併設されている。ＥＣＵ１０は、内燃機関１や排気浄化装置等を制御する。ＥＣＵ１０には、上述した各種センサの他、クランクポジションセンサ２１及びアクセル開度センサ２２が電気的に接続され、各センサの出力値がＥＣＵ１０に渡される。 The internal combustion engine 1 is provided with an ECU 10 which is an electronic control unit as a control device (controller). The ECU 10 controls the internal combustion engine 1, the exhaust gas purification device, and the like. In addition to the various sensors described above, the crank position sensor 21 and the accelerator opening sensor 22 are electrically connected to the ECU 10, and the output values of the sensors are passed to the ECU 10.

ＥＣＵ１０は、クランクポジションセンサ２１の検出に基づく機関回転速度や、アクセル開度センサ２２の検出に基づく機関負荷等の内燃機関１の運転状態を把握可能である。また、ＥＣＵ１０は、エアフローメータ２３の検出値及び燃料噴射弁６からの燃料噴射量に基づいて、排気の流量を算出することができる。一方、ＥＣＵ１０には、燃料噴射弁６が電気配線を介して接続されており、該ＥＣＵ１０により燃料噴射弁６が制御される。 The ECU 10 can grasp the operating state of the internal combustion engine 1 such as the engine rotation speed based on the detection of the crank position sensor 21 and the engine load based on the detection of the accelerator opening sensor 22. Further, the ECU 10 can calculate the flow rate of the exhaust gas based on the detected value of the air flow meter 23 and the fuel injection amount from the fuel injection valve 6. On the other hand, a fuel injection valve 6 is connected to the ECU 10 via electrical wiring, and the fuel injection valve 6 is controlled by the ECU 10.

ＥＣＵ１０は、空燃比センサ１１によって検出される空燃比（検出空燃比）と、比較対象となる空燃比と、を比較した結果に基づいて所定の処理を行う。例えば、ＥＣＵ１０は
、検出空燃比が目標空燃比となるように燃料噴射弁６からの燃料噴射量をフィードバック制御する。また、例えば、ＥＣＵ１０は、検出空燃比と閾値とを比較することにより、燃料噴射弁６の異常診断を行う。なお、本実施形態においてはＥＣＵ１０が所定の処理を行うことにより、本発明における処理装置として機能する。 The ECU 10 performs a predetermined process based on the result of comparing the air-fuel ratio (detected air-fuel ratio) detected by the air-fuel ratio sensor 11 and the air-fuel ratio to be compared. For example, the ECU 10 feedback-controls the fuel injection amount from the fuel injection valve 6 so that the detected air-fuel ratio becomes the target air-fuel ratio. Further, for example, the ECU 10 performs an abnormality diagnosis of the fuel injection valve 6 by comparing the detected air-fuel ratio with the threshold value. In the present embodiment, the ECU 10 performs a predetermined process to function as the processing device in the present invention.

図２は、空燃比センサ１１の検出素子主要部の断面構造を示した図である。空燃比センサ１１は、大気に通じているＡ室と、排気通路２の内部に通じているＢ室と、を隔てる固体電解質層１０１を備えている。固体電解質層１０１は、ジルコニア（Ｚｒ２Ｏ３）等の多孔質絶縁材料からなる。固体電解質層１０１のＡ室側壁面には、白金からなるＡ室側電極１０２が設けられており、固体電解質層１０１のＢ室側壁面には、白金からなるＢ室側電極１０３が設けられている。Ｂ室側電極１０３の表面は、拡散律速層１０４によって覆われており、排気通路２を流れる排気の一部が、拡散律速層１０４の内部を通過してＢ室側電極１０３に接触する。 FIG. 2 is a diagram showing a cross-sectional structure of a main part of the detection element of the air-fuel ratio sensor 11. The air-fuel ratio sensor 11 includes a solid electrolyte layer 101 that separates chamber A, which communicates with the atmosphere, and chamber B, which communicates with the inside of the exhaust passage 2. The solid electrolyte layer 101 is made of a porous insulating material such as zirconia (Zr 2 O 3 ). A chamber A side electrode 102 made of platinum is provided on the side wall surface of the chamber A of the solid electrolyte layer 101, and a chamber B side electrode 103 made of platinum is provided on the side wall surface of the chamber B of the solid electrolyte layer 101. There is. The surface of the B chamber side electrode 103 is covered with the diffusion controlled layer 104, and a part of the exhaust gas flowing through the exhaust passage 2 passes through the inside of the diffusion limited layer 104 and comes into contact with the B chamber side electrode 103.

このような構成の空燃比センサ１１において、Ａ室側電極１０２とＢ室側電極１０３との間にＥＣＵ１０により所定の電圧が印加されると、この電圧の印加によって空燃比センサ１１に排気中の酸素濃度に応じた電流が流れる。この電流は空燃比と相関があるため、この電流に基づいて空燃比センサ１１は空燃比を検出する。 In the air-fuel ratio sensor 11 having such a configuration, when a predetermined voltage is applied between the chamber A side electrode 102 and the chamber B side electrode 103 by the ECU 10, the application of this voltage causes the air-fuel ratio sensor 11 to be exhausted. An electric current flows according to the oxygen concentration. Since this current correlates with the air-fuel ratio, the air-fuel ratio sensor 11 detects the air-fuel ratio based on this current.

排気の空燃比が理論空燃比よりも大きな空燃比であるリーン空燃比である場合、燃料と反応せずに排気中に存在している酸素がＢ室側電極１０３での電極反応により電子を受け取ってイオン化される。その酸素イオンが固体電解質層１０１の内部をＢ室側電極１０３からＡ室側電極１０２へ向かって移動し、Ａ室側電極１０２に到達すると、そこで電子が離脱され酸素に戻ってＡ室に排出される。このような酸素イオンの移動によって、Ａ室側電極１０２からＢ室側電極１０３へ向かう方向に電流が流れる。 When the air-fuel ratio of the exhaust is a lean air-fuel ratio, which is a larger air-fuel ratio than the theoretical air-fuel ratio, oxygen existing in the exhaust without reacting with the fuel receives electrons by the electrode reaction at the electrode 103 on the B chamber side. Is ionized. The oxygen ions move inside the solid electrolyte layer 101 from the B chamber side electrode 103 toward the A chamber side electrode 102, and when they reach the A chamber side electrode 102, electrons are released there and returned to oxygen and discharged to the A chamber. Will be done. Due to such movement of oxygen ions, a current flows in the direction from the chamber A side electrode 102 to the chamber B side electrode 103.

一方、排気の空燃比が理論空燃比よりも小さな空燃比であるリッチ空燃比である場合、上述したリーン空燃比の場合とは逆に、Ａ室内の酸素がＡ室側電極１０２での電極反応により電子を受け取ってイオン化される。その酸素イオンが、固体電解質層１０１の内部をＡ室側電極１０２からＢ室側電極１０３へ向かって移動した後、拡散律速層１０４の内部で拡散された排気中の可燃成分（例えば、Ｈ２、ＣＯ、ＨＣなど）との触媒反応によりＣＯ２やＨ２Ｏが生成される。このような酸素イオンの移動によって、Ｂ室側電極１０３からＡ室側電極１０２へ向かう方向に電流が流れる。 On the other hand, when the air-fuel ratio of the exhaust is a rich air-fuel ratio, which is a smaller air-fuel ratio than the theoretical air-fuel ratio, the oxygen in the chamber A reacts with the electrode 102 on the chamber A side, contrary to the case of the lean air-fuel ratio described above. Receives electrons and is ionized. After the oxygen ions move inside the solid electrolyte layer 101 from the chamber A side electrode 102 toward the chamber B side electrode 103, the combustible component in the exhaust diffused inside the diffusion rate-determining layer 104 (for example, H 2). , CO, HC, etc.) to produce CO 2 and H 2 O. Due to such movement of oxygen ions, a current flows in the direction from the B chamber side electrode 103 to the A chamber side electrode 102.

このような空燃比センサ１１では、排気中に存在する水素により空燃比の検出誤差が生じる。水素は、排気中に含まれる酸素等の他の分子に比べて分子量が小さいため、拡散律速層１０４における拡散速度が速く、拡散律速層１０４を通過しやすい。すなわち、拡散律速層１０４を排気が通過する際に、水素濃度の低下は比較的小さいが、水素以外の他の分子の濃度の低下は大きくなる。そうすると、Ｂ室側電極１０３の近傍では、実際の排気（空燃比センサ１１に流入する前の排気）よりも、他の分子の濃度に対する水素濃度が相対的に高くなる。これにより、検出空燃比が実空燃比よりも小さくなる。この場合、排気の水素濃度が高いほど、実空燃比に対して検出空燃比が小さくなる。そこで、ＥＣＵ１０は、排気の水素濃度に応じて検出空燃比を補正する。 In such an air-fuel ratio sensor 11, an error in detecting the air-fuel ratio occurs due to hydrogen existing in the exhaust gas. Since hydrogen has a smaller molecular weight than other molecules such as oxygen contained in the exhaust, the diffusion rate in the diffusion-controlled layer 104 is high, and hydrogen easily passes through the diffusion-controlled layer 104. That is, when the exhaust gas passes through the diffusion-controlled layer 104, the decrease in hydrogen concentration is relatively small, but the decrease in concentration of molecules other than hydrogen is large. Then, in the vicinity of the B chamber side electrode 103, the hydrogen concentration with respect to the concentration of other molecules becomes relatively higher than the actual exhaust (exhaust before flowing into the air-fuel ratio sensor 11). As a result, the detected air-fuel ratio becomes smaller than the actual air-fuel ratio. In this case, the higher the hydrogen concentration in the exhaust gas, the smaller the detected air-fuel ratio with respect to the actual air-fuel ratio. Therefore, the ECU 10 corrects the detected air-fuel ratio according to the hydrogen concentration in the exhaust gas.

図３は、実際の排気の水素濃度と空燃比センサ１１の検出空燃比のずれ量（以下、検出空燃比ずれ量ともいう。）との関係を示した図である。検出空燃比ずれ量は、実空燃比から検出空燃比を減算した値を示している。排気の水素濃度が高くなるほど、検出空燃比が小さくなるため、排気の水素濃度が高くなるほど、検出空燃比ずれ量が大きくなる。したがって、排気の水素濃度が高いときには低いときよりも、検出空燃比を補正する際の補正量を空燃比がより大きくなる方向により大きくすることにより、実空燃比と検出空燃比と
の差を小さくすることができる。 FIG. 3 is a diagram showing the relationship between the actual hydrogen concentration of the exhaust gas and the deviation amount of the detected air-fuel ratio of the air-fuel ratio sensor 11 (hereinafter, also referred to as the detected air-fuel ratio deviation amount). The detected air-fuel ratio deviation amount indicates a value obtained by subtracting the detected air-fuel ratio from the actual air-fuel ratio. The higher the hydrogen concentration in the exhaust gas, the smaller the detected air-fuel ratio. Therefore, the higher the hydrogen concentration in the exhaust gas, the larger the detected air-fuel ratio deviation. Therefore, when the hydrogen concentration in the exhaust is high, the difference between the actual air-fuel ratio and the detected air-fuel ratio is made smaller by making the correction amount when correcting the detected air-fuel ratio larger in the direction in which the air-fuel ratio becomes larger than when it is low. can do.

しかし、排気の水素濃度に応じた検出空燃比の補正を行っても、検出空燃比が実空燃比からずれることがある。このようなずれは、空燃比センサ１１の応答性と相関があることが新たに見出された。ここで、空燃比センサ１１の応答性によって、水素による検出空燃比のずれやすさが変わる。この空燃比センサ１１の応答性は、個体差もあるが、空燃比センサ１１の使用過程において様々な要因で変化する。例えば、拡散律速層１０４の経時変化、煤による拡散律速層１０４の詰まり等によって、拡散律速層１０４におけるガスの拡散速度が変化し得る。そうすると、Ｂ室側電極１０３に到達する水素の量も経時的に変化し得る。したがって、図３に示した排気の水素濃度と検出空燃比ずれ量との相関が水素の拡散速度によって変化するため、排気の水素濃度に基づいて空燃比センサ１１の検出空燃比を補正しても、実空燃比と検出空燃比とのずれが残る。そこで、ＥＣＵ１０は、空燃比センサ１１の応答性を更に加味して検出空燃比を補正する。 However, even if the detected air-fuel ratio is corrected according to the hydrogen concentration of the exhaust gas, the detected air-fuel ratio may deviate from the actual air-fuel ratio. It was newly found that such a deviation correlates with the responsiveness of the air-fuel ratio sensor 11. Here, the susceptibility of the detected air-fuel ratio due to hydrogen changes depending on the responsiveness of the air-fuel ratio sensor 11. The responsiveness of the air-fuel ratio sensor 11 varies depending on various factors in the process of using the air-fuel ratio sensor 11, although there are individual differences. For example, the diffusion rate of gas in the diffusion-controlled layer 104 may change due to changes over time in the diffusion-controlled layer 104, clogging of the diffusion-controlled layer 104 with soot, and the like. Then, the amount of hydrogen reaching the B chamber side electrode 103 may also change with time. Therefore, since the correlation between the hydrogen concentration in the exhaust gas and the detected air-fuel ratio deviation amount shown in FIG. 3 changes depending on the hydrogen diffusion rate, even if the detected air-fuel ratio of the air-fuel ratio sensor 11 is corrected based on the hydrogen concentration in the exhaust gas. , The difference between the actual air-fuel ratio and the detected air-fuel ratio remains. Therefore, the ECU 10 corrects the detected air-fuel ratio by further considering the responsiveness of the air-fuel ratio sensor 11.

図４は、実際の排気の水素濃度と空燃比センサ１１の検出空燃比のずれ量（検出空燃比ずれ量）との関係を空燃比センサ１１の応答性毎に示した図である。同じ水素濃度で比較した場合、空燃比センサ１１の応答性が高いほど、検出空燃比ずれ量が大きくなる。また、空燃比センサ１１の応答性が同じであれば、排気の水素濃度が高くなるほど、検出空燃比ずれ量が大きくなる。図４に示した関係は実験またはシミュレーション等により求めることができる。 FIG. 4 is a diagram showing the relationship between the actual hydrogen concentration of the exhaust gas and the deviation amount of the detected air-fuel ratio of the air-fuel ratio sensor 11 (detected air-fuel ratio deviation amount) for each response of the air-fuel ratio sensor 11. When compared at the same hydrogen concentration, the higher the responsiveness of the air-fuel ratio sensor 11, the larger the detected air-fuel ratio deviation amount. Further, if the responsiveness of the air-fuel ratio sensor 11 is the same, the higher the hydrogen concentration in the exhaust gas, the larger the detected air-fuel ratio deviation amount. The relationship shown in FIG. 4 can be obtained by experiment or simulation.

次に、空燃比センサ１１の応答性の求め方について説明する。空燃比センサ１１の応答性は、実空燃比が変化してから検出空燃比がどの程度の速さで変化するのかを示しており、空燃比センサ１１の検出空燃比が変化したときの検出空燃比の時定数と反比例すると考える。なお、単位時間当たりの検出空燃比の変化量を応答性としてもよい。時定数は、検出空燃比が変化したときに、検出空燃比が該検出空燃比の最終値の例えば63.2％に達するまでの時間である。したがって、ＥＣＵ１０は、検出空燃比が変化したときの検出空燃比の推移を随時記憶している。そして、検出空燃比が増加した場合、ＥＣＵ１０は、検出空燃比の増加開始から増加終了までの期間における検出空燃比の変化量を算出し、検出空燃比の増加開始時点から、検出空燃比がその変化量の例えば63.2％に相当する値に達した時点までの時間を時定数として算出する。同様に、検出空燃比が減少した場合には、ＥＣＵ１０は、検出空燃比の減少開始から減少終了までの期間における検出空燃比の変化量を算出し、検出空燃比の減少開始時点から、検出空燃比がその変化量の63.2％に相当する値に達した時点までの時間を時定数として算出してもよい。 Next, how to obtain the responsiveness of the air-fuel ratio sensor 11 will be described. The responsiveness of the air-fuel ratio sensor 11 indicates how quickly the detected air-fuel ratio changes after the actual air-fuel ratio changes, and the detected air when the detected air-fuel ratio of the air-fuel ratio sensor 11 changes. It is considered to be inversely proportional to the time constant of the fuel ratio. The amount of change in the detected air-fuel ratio per unit time may be used as the responsiveness. The time constant is the time until the detected air-fuel ratio reaches, for example, 63.2% of the final value of the detected air-fuel ratio when the detected air-fuel ratio changes. Therefore, the ECU 10 stores the transition of the detected air-fuel ratio at any time when the detected air-fuel ratio changes. Then, when the detected air-fuel ratio increases, the ECU 10 calculates the amount of change in the detected air-fuel ratio during the period from the start of the increase in the detected air-fuel ratio to the end of the increase, and the detected air-fuel ratio becomes the detected air-fuel ratio from the time when the detected air-fuel ratio starts to increase. The time until the time when the value corresponding to, for example, 63.2% of the amount of change is reached is calculated as a time constant. Similarly, when the detected air-fuel ratio decreases, the ECU 10 calculates the amount of change in the detected air-fuel ratio during the period from the start of the decrease in the detected air-fuel ratio to the end of the decrease, and from the start of the decrease in the detected air-fuel ratio, the detected air-fuel ratio The time until the time when the fuel ratio reaches a value corresponding to 63.2% of the change amount may be calculated as a time constant.

なお、検出空燃比が１回上昇または下降したときに算出される時定数に反比例する値を応答性としてもよいが、この場合、外乱の影響が大きくなる。したがって、検出空燃比が複数回（例えば２〜３回）上昇または下降したときに夫々時定数を算出し、その平均値に反比例する値を応答性としてもよい。 The responsiveness may be a value inversely proportional to the time constant calculated when the detected air-fuel ratio rises or falls once, but in this case, the influence of disturbance becomes large. Therefore, when the detected air-fuel ratio rises or falls a plurality of times (for example, 2 to 3 times), the time constant may be calculated, and a value inversely proportional to the average value may be used as the responsiveness.

空燃比センサ１１の応答性を求めるためには、検出空燃比が変化する必要がある。この検出空燃比の変化は、成り行きによる検出空燃比の変化であってもよく、空燃比センサ１１の応答性を求めるためにＥＣＵ１０が空燃比を制御したことによる検出空燃比の変化であってもよい。また、空燃比センサ１１、触媒３、又はその他の装置の異常診断のためにＥＣＵ１０が空燃比を制御したことによる検出空燃比の変化であってもよい。例えば、減速時等に実施される燃料カットでは、燃料噴射弁６からの燃料噴射が停止されることにより、空燃比が大きく変化する。このような場合に検出空燃比の時定数を精度よく求めることができる。 In order to obtain the responsiveness of the air-fuel ratio sensor 11, the detected air-fuel ratio needs to be changed. This change in the detected air-fuel ratio may be a change in the detected air-fuel ratio due to the circumstances, or even a change in the detected air-fuel ratio due to the ECU 10 controlling the air-fuel ratio in order to obtain the responsiveness of the air-fuel ratio sensor 11. Good. Further, it may be a change in the detected air-fuel ratio due to the ECU 10 controlling the air-fuel ratio for abnormality diagnosis of the air-fuel ratio sensor 11, the catalyst 3, or other device. For example, in the fuel cut performed during deceleration or the like, the air-fuel ratio changes significantly by stopping the fuel injection from the fuel injection valve 6. In such a case, the time constant of the detected air-fuel ratio can be obtained accurately.

また、例えば、空燃比を、理論空燃比よりも大きな所定リーン空燃比と、理論空燃比よ
りも小さな所定リッチ空燃比とに交互に複数回変動させるアクティブ制御を実施したときには、空燃比が大きく変動する。このよう場合であっても、空燃比センサ１１の応答性を精度よく求めることができる。なお、空燃比センサ１１の応答性を求めるためにアクティブ制御を実施してもよいが、他の目的（例えば、異常診断）のためにアクティブ制御が実施されたときの検出空燃比を利用して空燃比センサ１１の応答性を求めてもよい。応答性を精度よく算出するためには、空燃比がある程度変化したほうが良い。したがって、応答性を精度よく算出可能なほど空燃比が変化したときに応答性を算出してもよい。 Further, for example, when active control is performed in which the air-fuel ratio is alternately changed a predetermined lean air-fuel ratio larger than the theoretical air-fuel ratio and a predetermined rich air-fuel ratio smaller than the theoretical air-fuel ratio a plurality of times, the air-fuel ratio fluctuates greatly. To do. Even in such a case, the responsiveness of the air-fuel ratio sensor 11 can be accurately obtained. Although active control may be performed to obtain the responsiveness of the air-fuel ratio sensor 11, the detected air-fuel ratio when active control is performed for another purpose (for example, abnormality diagnosis) may be used. The responsiveness of the air-fuel ratio sensor 11 may be obtained. In order to calculate the responsiveness accurately, it is better that the air-fuel ratio changes to some extent. Therefore, the responsiveness may be calculated when the air-fuel ratio changes so that the responsiveness can be calculated accurately.

応答性の算出は、内燃機関１の運転状態が所定の変化をしたときに行う。空燃比センサ１１の応答性は、空燃比等の内燃機関１の運転状態の影響を受けるため、内燃機関１の運転状態の変化の影響が応答性に表れないように、同じように内燃機関１の運転状態が変化したときの検出空燃比に基づいて応答性を算出する。なお、内燃機関１の運転状態が所定の変化とは異なる変化をしたときに算出された応答性を、運転状態が所定の変化をしたときの応答性となるように補正してもよい。また、所定の変化にはある程度の幅を持たせてもよいし、所定の変化を複数設定してもよい。 The responsiveness is calculated when the operating state of the internal combustion engine 1 changes by a predetermined value. Since the responsiveness of the air-fuel ratio sensor 11 is affected by the operating state of the internal combustion engine 1 such as the air-fuel ratio, the internal combustion engine 1 is similarly affected so that the influence of changes in the operating state of the internal combustion engine 1 does not appear in the responsiveness. The responsiveness is calculated based on the detected air-fuel ratio when the operating condition of the engine changes. The responsiveness calculated when the operating state of the internal combustion engine 1 changes differently from the predetermined change may be corrected so as to be the responsiveness when the operating state changes a predetermined change. Further, the predetermined change may have a certain range, or a plurality of predetermined changes may be set.

上記のように、空燃比センサ１１の応答性は、検出空燃比が水素によって実空燃比からずれるときのずれやすさと相関がある。そのため、検出空燃比を補正するときに、排気の水素濃度に加えて、空燃比センサ１１の応答性を考慮する。図５は、応答性と水素濃度と検出空燃比ずれ量との関係を示した図である。水素濃度と検出空燃比のずれ量とを一次関数（検出空燃比ずれ量＝ＲＥ・水素濃度）で表している。ここで、ＲＥは、応答性に応じて変わる係数であり、この係数ＲＥは、応答性が高いほど大きくなる。応答性と係数ＲＥとの関係は、予め実験またはシミュレーション等により求めてＥＣＵ１０に記憶される。 As described above, the responsiveness of the air-fuel ratio sensor 11 correlates with the susceptibility to deviation when the detected air-fuel ratio deviates from the actual air-fuel ratio due to hydrogen. Therefore, when correcting the detected air-fuel ratio, the responsiveness of the air-fuel ratio sensor 11 is taken into consideration in addition to the hydrogen concentration in the exhaust gas. FIG. 5 is a diagram showing the relationship between the responsiveness, the hydrogen concentration, and the detected air-fuel ratio deviation amount. The difference between the hydrogen concentration and the detected air-fuel ratio is represented by a linear function (detected air-fuel ratio deviation = RE / hydrogen concentration). Here, RE is a coefficient that changes according to the responsiveness, and the coefficient RE increases as the responsiveness increases. The relationship between the responsiveness and the coefficient RE is obtained in advance by an experiment, simulation, or the like and stored in the ECU 10.

なお、図５では、水素濃度と検出空燃比ずれ量との関係を簡易的に一時関数で表しているが、これに代えて、図４に示したように実験等によって求まる関係を用いて、水素濃度と検出空燃比ずれ量との相関を得てもよい。 In FIG. 5, the relationship between the hydrogen concentration and the detected air-fuel ratio deviation amount is simply represented by a temporary function, but instead, as shown in FIG. 4, the relationship obtained by experiments or the like is used. A correlation between the hydrogen concentration and the detected air-fuel ratio deviation may be obtained.

以上のようにして求まる検出空燃比ずれ量を、検出空燃比の補正量として用いる。すなわち、検出空燃比に検出空燃比ずれ量を加算することにより検出空燃比を補正する。検出空燃比の補正は、水素が発生していると推定されるときに行う。なお、上記説明では、検出空燃比に加算して検出空燃比を補正する補正量を求めているが、これに代えて、検出空燃比に乗算して検出空燃比を補正する補正係数を求めるようにしてもよい。 The detected air-fuel ratio deviation amount obtained as described above is used as the correction amount of the detected air-fuel ratio. That is, the detected air-fuel ratio is corrected by adding the detected air-fuel ratio deviation amount to the detected air-fuel ratio. The detected air-fuel ratio is corrected when it is estimated that hydrogen is being generated. In the above description, the correction amount for correcting the detected air-fuel ratio by adding it to the detected air-fuel ratio is obtained. Instead, the correction coefficient for correcting the detected air-fuel ratio is obtained by multiplying the detected air-fuel ratio. It may be.

図６は、検出空燃比を補正するときの各種値の推移を示したタイムチャートである。上から順に、機関回転速度、燃料噴射弁６からの燃料噴射量、検出空燃比、空燃比センサ１１の応答性の算出値、排気の水素濃度の推定値、検出空燃比の補正量を示している。検出空燃比における破線は、補正後の検出空燃比を示しており、検出空燃比における実線は、補正前の検出空燃比を示している。 FIG. 6 is a time chart showing changes in various values when the detected air-fuel ratio is corrected. From the top, the engine speed, the fuel injection amount from the fuel injection valve 6, the detected air-fuel ratio, the calculated value of the responsiveness of the air-fuel ratio sensor 11, the estimated value of the hydrogen concentration in the exhaust, and the correction amount of the detected air-fuel ratio are shown. There is. The broken line in the detected air-fuel ratio indicates the detected air-fuel ratio after correction, and the solid line in the detected air-fuel ratio indicates the detected air-fuel ratio before correction.

Ｔ１からＴ２の期間においてアクティブ制御が実施されており、燃料噴射量が同期的に増減されている。これによって、検出空燃比が変動している。この期間の検出空燃比に基づいて空燃比センサ１１の応答性を算出している。 Active control is carried out during the period from T1 to T2, and the fuel injection amount is increased or decreased synchronously. As a result, the detected air-fuel ratio fluctuates. The responsiveness of the air-fuel ratio sensor 11 is calculated based on the detected air-fuel ratio during this period.

排気の水素濃度は、内燃機関１の負荷と関連性を有することから、内燃機関１の負荷に基づいて排気の水素濃度を推定することができる。内燃機関１の負荷と排気の水素濃度との関係を予め実験またはシミュレーション等により求めてＥＣＵ１０に記憶させておけば、内燃機関１の負荷に基づいて排気の水素濃度を推定することができる。また、排気の水素濃度は、他のパラメータに基づいて推定することもできる。例えば、吸入空気量及び燃料噴射量、または、吸入空気量及び空燃比も排気の水素濃度と関連性を有する。また、排
気温度が高いほど、排気中の水素と酸素とが反応し易くなって水素が減少することから、水素濃度が低下する。したがって、排気温度と水素濃度とにも相関があるため、排気温度に基づいて水素濃度を推定することもできる。この場合、排気温度が低いときには高いときよりも水素濃度が高くなるように推定する。なお、排気の温度が所定温度以上の場合には、水素濃度を０としてもよい。この所定温度は、水素と酸素との反応が進んで排気中に水素が存在しなくなる温度である。これら排気の水素濃度と相関のあるパラメータを複数組み合わせて排気の水素濃度を推定してもよい。このようにして、ＥＣＵ１０は、水素濃度を随時推定する。なお、排気の水素濃度は上記に限らず他の手段により得てもよい。例えば、センサを用いて水素濃度を検出してもよい。 Since the hydrogen concentration in the exhaust gas is related to the load of the internal combustion engine 1, the hydrogen concentration in the exhaust gas can be estimated based on the load of the internal combustion engine 1. If the relationship between the load of the internal combustion engine 1 and the hydrogen concentration of the exhaust gas is obtained in advance by an experiment or simulation and stored in the ECU 10, the hydrogen concentration of the exhaust gas can be estimated based on the load of the internal combustion engine 1. The hydrogen concentration in the exhaust can also be estimated based on other parameters. For example, the intake air amount and the fuel injection amount, or the intake air amount and the air-fuel ratio are also related to the hydrogen concentration of the exhaust gas. Further, the higher the exhaust temperature, the easier it is for hydrogen and oxygen in the exhaust to react and the amount of hydrogen decreases, so that the hydrogen concentration decreases. Therefore, since there is a correlation between the exhaust temperature and the hydrogen concentration, the hydrogen concentration can be estimated based on the exhaust temperature. In this case, it is estimated that the hydrogen concentration is higher when the exhaust temperature is low than when it is high. When the exhaust temperature is equal to or higher than the predetermined temperature, the hydrogen concentration may be set to 0. This predetermined temperature is a temperature at which the reaction between hydrogen and oxygen proceeds and hydrogen does not exist in the exhaust gas. The hydrogen concentration of the exhaust gas may be estimated by combining a plurality of parameters that correlate with the hydrogen concentration of the exhaust gas. In this way, the ECU 10 estimates the hydrogen concentration at any time. The hydrogen concentration in the exhaust gas is not limited to the above and may be obtained by other means. For example, a sensor may be used to detect the hydrogen concentration.

ここで、図５に示したように、内燃機関１の運転状態（例えば、機関回転速度及び機関負荷）が同じであれば（すなわち、水素濃度が同じであれば）、応答性が高いほど、検出空燃比ずれ量が大きくなる。ＥＣＵ１０は、図６におけるＴ１からＴ２の期間において算出された応答性に対応する係数ＲＥを読み込み、Ｔ２以降において推定される水素濃度に係数ＲＥを乗算して検出空燃比ずれ量、すなわち、検出空燃比の補正量を算出する。ＥＣＵ１０は、検出空燃比に検出空燃比ずれ量を加算することにより、検出空燃比を補正する。 Here, as shown in FIG. 5, if the operating state of the internal combustion engine 1 (for example, the engine rotation speed and the engine load) is the same (that is, if the hydrogen concentration is the same), the higher the responsiveness, the higher the responsiveness. The amount of detected air-fuel ratio deviation increases. The ECU 10 reads the coefficient RE corresponding to the responsiveness calculated in the period from T1 to T2 in FIG. 6, and multiplies the hydrogen concentration estimated after T2 by the coefficient RE to detect the air-fuel ratio deviation amount, that is, the detected air-fuel ratio. Calculate the fuel ratio correction amount. The ECU 10 corrects the detected air-fuel ratio by adding the detected air-fuel ratio deviation amount to the detected air-fuel ratio.

図６においてＴ２からＴ３の期間では、水素濃度の推定値が０であるため、係数ＲＥが０となり、検出空燃比の補正量も０となる。Ｔ３以降に機関回転速度及び燃料噴射量が増加して水素濃度の推定値が増加すると、この水素濃度の推定値と、係数ＲＥと、に基づいて、補正量が算出される。そのため、Ｔ３以降では、補正量が水素濃度の推定値に応じて増加している。この補正量にしたがって補正された検出空燃比は、補正前の検出空燃比よりも大きくなる。すなわち、水素の影響により検出空燃比が実空燃比よりも小さくなるため、これを解消するように、検出空燃比が大きくなるように補正される。 In the period from T2 to T3 in FIG. 6, since the estimated value of the hydrogen concentration is 0, the coefficient RE is 0 and the correction amount of the detected air-fuel ratio is also 0. When the engine speed and the fuel injection amount increase after T3 and the estimated value of the hydrogen concentration increases, the correction amount is calculated based on the estimated value of the hydrogen concentration and the coefficient RE. Therefore, after T3, the correction amount increases according to the estimated value of the hydrogen concentration. The detected air-fuel ratio corrected according to this correction amount becomes larger than the detected air-fuel ratio before correction. That is, since the detected air-fuel ratio becomes smaller than the actual air-fuel ratio due to the influence of hydrogen, it is corrected so that the detected air-fuel ratio becomes larger so as to eliminate this.

図７は、係数ＲＥを求めるためのフローチャートである。本フローチャートは、ＥＣＵ１０により所定の時間毎に実行される。なお、空燃比センサ１１の応答性は拡散律速層１０４の状況によって変動するので、所定の間隔で係数ＲＥを求めることが好ましい。 FIG. 7 is a flowchart for obtaining the coefficient RE. This flowchart is executed by the ECU 10 at predetermined time intervals. Since the responsiveness of the air-fuel ratio sensor 11 varies depending on the condition of the diffusion-controlled layer 104, it is preferable to obtain the coefficient RE at predetermined intervals.

ステップＳ１０１では、応答性を求める前提条件が成立しているか否か判定される。燃料カット又はアクティブ制御が開始され、且つ、内燃機関１の運転状態が所定の変化をした場合に、前提条件が成立していると判定される。すなわち、燃料カット又はアクティブ制御が開始された場合には、空燃比センサ１１の時定数を求めることができる状態であるため、燃料カット又はアクティブ制御が開始されたことを前提条件の１つにしている。また、応答性の算出値は、内燃機関１の運転状態の影響を受けるため、内燃機関１の運転状態が所定の変化をしたときに応答性を算出する。すなわち、内燃機関１の運転状態が所定の変化をしたことを前提条件の１つにしている。ステップＳ１０１で肯定判定がなされた場合にはステップＳ１０２へ進み、一方、否定判定がなされた場合には本フローチャートを終了させる。 In step S101, it is determined whether or not the precondition for obtaining responsiveness is satisfied. When the fuel cut or active control is started and the operating state of the internal combustion engine 1 changes by a predetermined value, it is determined that the precondition is satisfied. That is, when the fuel cut or active control is started, the time constant of the air-fuel ratio sensor 11 can be obtained. Therefore, it is one of the preconditions that the fuel cut or active control is started. There is. Further, since the calculated value of the responsiveness is affected by the operating state of the internal combustion engine 1, the responsiveness is calculated when the operating state of the internal combustion engine 1 changes by a predetermined value. That is, one of the preconditions is that the operating state of the internal combustion engine 1 has changed by a predetermined value. If an affirmative determination is made in step S101, the process proceeds to step S102, while if a negative determination is made, this flowchart is terminated.

ステップＳ１０２では、空燃比センサ１１の応答性が算出され、ステップＳ１０３では、係数ＲＥが算出される。空燃比センサ１１の応答性と係数ＲＥとの関係は予めＥＣＵ１０に記憶されている。ステップＳ１０３で求められた係数ＲＥは、水素濃度に乗算して検出空燃比の補正量を求めるための係数ＲＥとしてＥＣＵ１０により記憶される。なお、ステップＳ１０１で否定判定がなされた場合には、過去に求められた係数ＲＥに基づいて、検出空燃比の補正が行われる。 In step S102, the responsiveness of the air-fuel ratio sensor 11 is calculated, and in step S103, the coefficient RE is calculated. The relationship between the responsiveness of the air-fuel ratio sensor 11 and the coefficient RE is stored in the ECU 10 in advance. The coefficient RE obtained in step S103 is stored by the ECU 10 as a coefficient RE for multiplying the hydrogen concentration to obtain the correction amount of the detected air-fuel ratio. If a negative determination is made in step S101, the detected air-fuel ratio is corrected based on the coefficient RE obtained in the past.

次に、図８は、検出空燃比の補正を行うフローを示したフローチャートである。本フローチャートは、ＥＣＵ１０により所定の時間毎に実行される。 Next, FIG. 8 is a flowchart showing a flow for correcting the detected air-fuel ratio. This flowchart is executed by the ECU 10 at predetermined time intervals.

ステップＳ２０１では、排気の水素濃度が読み込まれる。ＥＣＵ１０は、上記のように内燃機関１の負荷、排気温度等のパラメータを用いて排気の水素濃度を随時算出しているため、この値が読み込まれる。 In step S201, the hydrogen concentration of the exhaust is read. Since the ECU 10 calculates the hydrogen concentration of the exhaust gas at any time using parameters such as the load of the internal combustion engine 1 and the exhaust gas temperature as described above, this value is read.

ステップＳ２０２では、水素濃度に応じて検出空燃比の補正が行われる。このときには、ステップＳ２０１で読み込まれた排気の水素濃度に、ステップＳ１０３で算出された係数ＲＥを乗算することにより、検出空燃比ずれ量が算出され、この検出空燃比ずれ量を検出空燃比に加算することにより、検出空燃比の補正が行われる。なお、本実施形態においてはＥＣＵ１０がステップＳ２０２を処理することにより、本発明における制御装置として機能する。 In step S202, the detected air-fuel ratio is corrected according to the hydrogen concentration. At this time, the detected air-fuel ratio deviation amount is calculated by multiplying the hydrogen concentration of the exhaust gas read in step S201 by the coefficient RE calculated in step S103, and this detected air-fuel ratio deviation amount is added to the detected air-fuel ratio. By doing so, the detected air-fuel ratio is corrected. In the present embodiment, the ECU 10 processes step S202 to function as the control device in the present invention.

このようにして、空燃比センサ１１の応答性及び排気の水素濃度に基づいて、検出空燃比の補正を行うことができるため、より正確な空燃比の取得が可能となる。これにより、補正後の検出空燃比を用いて、精度の高い空燃比制御や精度の高い異常診断を実施することができる。 In this way, the detected air-fuel ratio can be corrected based on the responsiveness of the air-fuel ratio sensor 11 and the hydrogen concentration in the exhaust gas, so that a more accurate air-fuel ratio can be obtained. As a result, it is possible to carry out highly accurate air-fuel ratio control and highly accurate abnormality diagnosis using the corrected detected air-fuel ratio.

以上の説明では、検出空燃比の補正を行っているが、これに代えて、空燃比センサ１１を用いた制御時に検出空燃比と比較する空燃比（制御目標値や閾値）を補正してもよい。例えば、空燃比制御における目標空燃比を補正する場合には、空燃比センサ１１の応答性が高いときは低いときよりも、目標空燃比の補正量を空燃比が小さくなる側により大きくする。 In the above description, the detected air-fuel ratio is corrected, but instead of this, the air-fuel ratio (control target value or threshold value) to be compared with the detected air-fuel ratio during control using the air-fuel ratio sensor 11 can be corrected. Good. For example, when correcting the target air-fuel ratio in the air-fuel ratio control, the correction amount of the target air-fuel ratio is made larger on the side where the air-fuel ratio becomes smaller than when the response of the air-fuel ratio sensor 11 is high.

ここで、空燃比フィードバック制御時には検出空燃比が目標空燃比となるように燃料噴射弁６からの燃料噴射量または吸入空気量が調整される。検出空燃比が排気中の水素によって実際の空燃比からずれている場合には、検出空燃比を補正することにより精度の高い空燃比制御が可能となるが、目標空燃比を補正することによっても同様に精度の高い空燃比制御が可能となる。すなわち、図５に基づいて算出される検出空燃比ずれ量を、検出空燃比に加算する代わりに、目標空燃比から減算しても、空燃比フィードバック制御における燃料噴射量や吸入空気量の調整量は同じになるため、所望の空燃比に調整できることに変わりはない。 Here, during the air-fuel ratio feedback control, the fuel injection amount or the intake air amount from the fuel injection valve 6 is adjusted so that the detected air-fuel ratio becomes the target air-fuel ratio. If the detected air-fuel ratio deviates from the actual air-fuel ratio due to hydrogen in the exhaust, it is possible to control the air-fuel ratio with high accuracy by correcting the detected air-fuel ratio, but it is also possible to correct the target air-fuel ratio. Similarly, highly accurate air-fuel ratio control becomes possible. That is, even if the detected air-fuel ratio deviation amount calculated based on FIG. 5 is subtracted from the target air-fuel ratio instead of being added to the detected air-fuel ratio, the fuel injection amount and the intake air amount are adjusted in the air-fuel ratio feedback control. Will be the same, so it is still possible to adjust to the desired air-fuel ratio.

図９は、目標空燃比の補正を行うフローを示したフローチャートである。本フローチャートは、ＥＣＵ１０により所定の時間毎に実行される。 FIG. 9 is a flowchart showing a flow for correcting the target air-fuel ratio. This flowchart is executed by the ECU 10 at predetermined time intervals.

ステップＳ３０１では、排気の水素濃度が読み込まれる。ＥＣＵ１０は、排気の水素濃度を随時算出しているため、この値が読み込まれる。 In step S301, the hydrogen concentration of the exhaust gas is read. Since the ECU 10 calculates the hydrogen concentration of the exhaust gas at any time, this value is read.

ステップＳ３０２では、水素濃度に応じて目標空燃比の補正が行われる。このときには、ステップＳ２０１で読み込まれた排気の水素濃度に、ステップＳ１０３で算出された係数ＲＥを乗算することにより、検出空燃比ずれ量が算出され、この検出空燃比ずれ量を目標空燃比から減算することにより、目標空燃比の補正が行われる。なお、本実施形態においてはＥＣＵ１０がステップＳ３０２を処理することにより、本発明における制御装置として機能する。 In step S302, the target air-fuel ratio is corrected according to the hydrogen concentration. At this time, the detected air-fuel ratio deviation amount is calculated by multiplying the hydrogen concentration of the exhaust gas read in step S201 by the coefficient RE calculated in step S103, and the detected air-fuel ratio deviation amount is subtracted from the target air-fuel ratio. By doing so, the target air-fuel ratio is corrected. In the present embodiment, the ECU 10 processes step S302 to function as the control device in the present invention.

図１０は、目標となる空気過剰率λを、排気の水素濃度及び検出空燃比の時定数毎に示した図である。排気の水素濃度が高くなるほど、また、時定数が小さくなるほど（センサの応答性が高くなるほど）、目標となる空気過剰率λが大きくなるように空燃比（燃料噴射量または吸入空気量）を調整する。このように、検出空燃比の代わりに、制御目標値を補正することもできる。 FIG. 10 is a diagram showing a target excess air ratio λ for each time constant of the hydrogen concentration of the exhaust gas and the detected air-fuel ratio. Adjust the air-fuel ratio (fuel injection amount or intake air amount) so that the target air excess rate λ increases as the hydrogen concentration in the exhaust increases and the time constant decreases (the sensor response increases). To do. In this way, the control target value can be corrected instead of the detected air-fuel ratio.

また、検出空燃比と閾値とを比較して、例えば、燃料噴射弁６の異常診断を実施する場合や、各種センサの異常診断を実施する場合、空燃比センサ１１よりも上流に備わる各種装置の異常診断を実施する場合等には、検出空燃比を補正する代わりに閾値を補正してもよい。すなわち、図５に基づいて算出される検出空燃比ずれ量を、検出空燃比に加算する代わりに、閾値から減算しても、空燃比センサ１１の応答性及び水素による影響を軽減することができる。この場合には、空燃比センサ１１の応答性が高いときは低いときよりも、閾値の補正量を空燃比が小さくなる側により大きくする。 Further, when comparing the detected air-fuel ratio with the threshold value, for example, when performing an abnormality diagnosis of the fuel injection valve 6 or performing an abnormality diagnosis of various sensors, various devices provided upstream of the air-fuel ratio sensor 11 When performing an abnormality diagnosis or the like, the threshold value may be corrected instead of correcting the detected air-fuel ratio. That is, even if the detected air-fuel ratio deviation amount calculated based on FIG. 5 is subtracted from the threshold value instead of being added to the detected air-fuel ratio, the responsiveness of the air-fuel ratio sensor 11 and the influence of hydrogen can be reduced. .. In this case, when the responsiveness of the air-fuel ratio sensor 11 is high, the correction amount of the threshold value is made larger on the side where the air-fuel ratio becomes smaller than when it is low.

以上の説明では排気の水素濃度を推定し、この水素濃度に基づいて検出空燃比、または検出空燃比と比較する空燃比（制御目標値や閾値）の補正を行っているが、排気の水素濃度は必ずしも直接推定する必要はない。例えば、排気の水素濃度と相関のあるパラメータを用いて検出空燃比の補正や、検出空燃比と比較する空燃比（制御目標値や閾値）の補正を行ってもよい。例えば、内燃機関１の負荷は排気の水素濃度と相関があるため、内燃機関１の負荷から検出空燃比の補正を直接行ってもよい。この場合、内燃機関１の負荷と、応答性と、検出空燃比の補正量との関係を、予め実験またはシミュレーション等により求めておく。 In the above explanation, the hydrogen concentration of the exhaust gas is estimated, and the detected air-fuel ratio or the air-fuel ratio (control target value or threshold value) to be compared with the detected air-fuel ratio is corrected based on this hydrogen concentration. Does not necessarily have to be estimated directly. For example, the detected air-fuel ratio may be corrected by using a parameter correlated with the hydrogen concentration of the exhaust gas, or the air-fuel ratio (control target value or threshold value) to be compared with the detected air-fuel ratio may be corrected. For example, since the load of the internal combustion engine 1 correlates with the hydrogen concentration of the exhaust gas, the detected air-fuel ratio may be directly corrected from the load of the internal combustion engine 1. In this case, the relationship between the load of the internal combustion engine 1, the responsiveness, and the correction amount of the detected air-fuel ratio is obtained in advance by an experiment, a simulation, or the like.

また、例えば、吸入空気量及び空燃比は排気の水素濃度と相関があるため、吸入空気量及び空燃比から検出空燃比の補正を直接行ってもよい。この場合、吸入空気量及び空燃比と、空燃比センサ１１の応答性と、検出空燃比の補正量との関係を、予め実験またはシミュレーション等により求めておく。同様に、排気温度も排気の水素濃度と相関があるため、排気温度から検出空燃比の補正を直接行ってもよい。この場合、排気温度が低いときには高いときよりも、補正量を大きくする。このような補正を行う場合には、排気温度と、空燃比センサ１１の応答性と、検出空燃比の補正量との関係を、予め実験またはシミュレーション等により求めておく。なお、排気の温度が所定温度以上の場合には、補正量を０としてもよい。この所定温度は、水素と酸素との反応が進んで排気中に水素が存在しなくなる温度である。また、内燃機関１の負荷、吸入空気量、燃料噴射量、空燃比、排気温度などの水素濃度と相関があるパラメータのうちの２つ以上を組み合わせて検出空燃比の補正を直接行ってもよい。 Further, for example, since the intake air amount and the air-fuel ratio correlate with the hydrogen concentration of the exhaust gas, the detected air-fuel ratio may be directly corrected from the intake air amount and the air-fuel ratio. In this case, the relationship between the intake air amount and the air-fuel ratio, the responsiveness of the air-fuel ratio sensor 11, and the correction amount of the detected air-fuel ratio is obtained in advance by an experiment or simulation. Similarly, since the exhaust temperature also correlates with the hydrogen concentration of the exhaust, the detected air-fuel ratio may be directly corrected from the exhaust temperature. In this case, when the exhaust temperature is low, the correction amount is larger than when the exhaust temperature is high. When making such a correction, the relationship between the exhaust temperature, the responsiveness of the air-fuel ratio sensor 11, and the corrected amount of the detected air-fuel ratio is obtained in advance by an experiment or simulation. When the exhaust temperature is equal to or higher than the predetermined temperature, the correction amount may be set to 0. This predetermined temperature is a temperature at which the reaction between hydrogen and oxygen proceeds and hydrogen does not exist in the exhaust gas. Further, the detected air-fuel ratio may be directly corrected by combining two or more of the parameters correlating with the hydrogen concentration such as the load of the internal combustion engine 1, the intake air amount, the fuel injection amount, the air-fuel ratio, and the exhaust temperature. ..

また、上記説明では、排気の水素濃度及び空燃比センサ１１の応答性に基づいて検出空燃比の補正を行っているが、これに代えて、排気の水素濃度を用いずに検出空燃比の補正を行ってもよい。この場合、空燃比センサ１１の応答性に基づいた検出空燃比の補正を行う。補正に排気の水素濃度を用いない場合、排気の水素濃度を推定する必要がない。また、水素濃度によらずに補正を行うため、排気中に水素が存在しないときも含めて補正を行う。例えば、空燃比センサ１１の応答性を算出し、その応答性に対応する係数ＲＥを求める。そして、内燃機関１の運転状態に関わらず、排気の水素濃度が所定の水素濃度であると仮定して検出空燃比のずれ量を算出し、検出空燃比、または、検出空燃比と比較する空燃比（制御目標値や閾値）の補正を行う。補正量が求まれば、排気の水素濃度によらず、補正量は一定となる。すなわち、補正量は空燃比センサ１１の応答性によって変化するが、排気の水素濃度によっては変化しない。ここでいう所定の水素濃度は、例えば、内燃機関１の運転状態に応じて変化し得る水素濃度の平均値としてもよいし、エミッションが良好となるように定めてもよい。このようにして、水素濃度に基づいた補正を行う必要が無くなるため処理が簡単になる。なお、排気の水素濃度を用いた補正を行う運転領域と、排気の水素濃度を用いない補正を行う運転領域と、を分けてもよい。 Further, in the above description, the detected air-fuel ratio is corrected based on the hydrogen concentration of the exhaust gas and the responsiveness of the air-fuel ratio sensor 11. Instead, the detected air-fuel ratio is corrected without using the hydrogen concentration of the exhaust gas. May be done. In this case, the detected air-fuel ratio is corrected based on the responsiveness of the air-fuel ratio sensor 11. When the hydrogen concentration of the exhaust is not used for the correction, it is not necessary to estimate the hydrogen concentration of the exhaust. In addition, since the correction is performed regardless of the hydrogen concentration, the correction is performed even when hydrogen is not present in the exhaust gas. For example, the responsiveness of the air-fuel ratio sensor 11 is calculated, and the coefficient RE corresponding to the responsiveness is obtained. Then, regardless of the operating state of the internal combustion engine 1, the deviation amount of the detected air-fuel ratio is calculated on the assumption that the hydrogen concentration of the exhaust gas is a predetermined hydrogen concentration, and the detected air-fuel ratio or the air to be compared with the detected air-fuel ratio is compared. Correct the fuel ratio (control target value and threshold value). If the correction amount is obtained, the correction amount will be constant regardless of the hydrogen concentration in the exhaust gas. That is, the correction amount changes depending on the responsiveness of the air-fuel ratio sensor 11, but does not change depending on the hydrogen concentration in the exhaust gas. The predetermined hydrogen concentration referred to here may be, for example, an average value of hydrogen concentrations that can change depending on the operating state of the internal combustion engine 1, or may be set so as to have good emissions. In this way, it is not necessary to make a correction based on the hydrogen concentration, which simplifies the process. The operating region for correction using the hydrogen concentration of the exhaust gas and the operating region for correction using the hydrogen concentration of the exhaust gas may be separated.

また、上記説明では、空燃比センサ１１の応答性（時定数としてもよい）を直接用いて検出空燃比の補正を行っているが、これに代えて、空燃比センサ１１の応答性と相関するパラメータを用いて検出空燃比の補正を行ってもよい。空燃比センサ１１の応答性と相関
するパラメータとして、応答性の基準値と応答性の算出値との差または比を用いてもよい。応答性の基準値は、例えば、空燃比センサ１１の新品時に想定される応答性であり、複数の空燃比センサ１１の新品時の応答性を予め実験またはシミュレーション等により求めて平均値を算出し、この平均値を応答性の基準値として設定しておく。このようにして設定される応答性の基準値は、空燃比センサ１１の個体差に関係なく一定の値であるが、これに代えて、空燃比センサ１１の新品時に実際に求めた応答性をその空燃比センサ１１の基準値として設定してもよい。応答性の基準値と応答性の算出値との差または比、排気の水素濃度、検出空燃比の補正量、との関係は、予め実験またはシミュレーション等により求めておく。 Further, in the above description, the detected air-fuel ratio is corrected by directly using the responsiveness (may be a time constant) of the air-fuel ratio sensor 11, but instead, it correlates with the responsiveness of the air-fuel ratio sensor 11. The detected air-fuel ratio may be corrected using parameters. As a parameter that correlates with the responsiveness of the air-fuel ratio sensor 11, the difference or ratio between the responsiveness reference value and the responsiveness calculated value may be used. The reference value of responsiveness is, for example, the responsiveness assumed when the air-fuel ratio sensor 11 is new, and the responsiveness of a plurality of air-fuel ratio sensors 11 when new is obtained in advance by experiments or simulations, and the average value is calculated. , This average value is set as a reference value for responsiveness. The reference value of the responsiveness set in this way is a constant value regardless of the individual difference of the air-fuel ratio sensor 11, but instead, the responsiveness actually obtained when the air-fuel ratio sensor 11 is new is obtained. It may be set as a reference value of the air-fuel ratio sensor 11. The relationship between the difference or ratio between the responsiveness reference value and the responsiveness calculated value, the hydrogen concentration in the exhaust gas, and the correction amount of the detected air-fuel ratio is obtained in advance by experiments or simulations.

以上のように、本実施形態によれば、検出空燃比、または、検出空燃比と比較する空燃比（制御目標値や閾値）を空燃比センサ１１の応答性に基づいて補正することにより、水素による空燃比センサ１１の検出値のずれの影響を軽減することができる。 As described above, according to the present embodiment, hydrogen is corrected by correcting the detected air-fuel ratio or the air-fuel ratio (control target value or threshold value) to be compared with the detected air-fuel ratio based on the responsiveness of the air-fuel ratio sensor 11. It is possible to reduce the influence of the deviation of the detected value of the air-fuel ratio sensor 11 due to the above.

１ 内燃機関
２ 排気通路
３ 触媒
６ 燃料噴射弁
１１ 空燃比センサ 1 Internal combustion engine 2 Exhaust passage 3 Catalyst 6 Fuel injection valve 11 Air-fuel ratio sensor

Claims (5)

内燃機関の排気通路に設けられ拡散律速層を有し排気の空燃比を検出する酸素センサと、
前記酸素センサの検出値を補正する制御装置であって、前記内燃機関の運転状態が同じ状態の下では、前記内燃機関の空燃比が変化したときの前記酸素センサの応答性が、高いときは低いときよりも、前記酸素センサの検出値の補正量を空燃比が大きくなる側により大きくする制御装置と、
を備える内燃機関の排気装置。 An oxygen sensor that is installed in the exhaust passage of an internal combustion engine and has a diffusion-controlled layer to detect the air-fuel ratio of the exhaust.
A control device that corrects the detection value of the oxygen sensor, and when the response of the oxygen sensor is high when the air-fuel ratio of the internal combustion engine changes under the same operating state of the internal combustion engine. A control device that makes the correction amount of the detected value of the oxygen sensor larger on the side where the air-fuel ratio is larger than when it is low.
An exhaust system for an internal combustion engine. 内燃機関の排気通路に設けられ拡散律速層を有し排気の空燃比を検出する酸素センサと、
前記酸素センサにより検出される空燃比と、比較対象となる空燃比と、を比較した結果に基づいて所定の処理を行う処理装置と、
前記比較対象となる空燃比を補正する制御装置であって、前記内燃機関の運転状態が同じ状態の下では、前記内燃機関の空燃比が変化したときの前記酸素センサの応答性が、高いときは低いときよりも、前記比較対象となる空燃比の補正量を空燃比が小さくなる側により大きくする制御装置と、
を備える内燃機関の排気装置。 An oxygen sensor that is installed in the exhaust passage of an internal combustion engine and has a diffusion-controlled layer to detect the air-fuel ratio of the exhaust.
A processing device that performs a predetermined process based on the result of comparing the air-fuel ratio detected by the oxygen sensor and the air-fuel ratio to be compared.
A control device that corrects the air-fuel ratio to be compared, and when the responsiveness of the oxygen sensor when the air-fuel ratio of the internal combustion engine changes is high under the same operating state of the internal combustion engine. Is a control device that makes the correction amount of the air-fuel ratio to be compared larger on the side where the air-fuel ratio becomes smaller than when it is low.
An exhaust system for an internal combustion engine. 前記制御装置は、排気の水素濃度が高いときは低いときよりも、補正量を大きくする請求項１または２に記載の内燃機関の排気装置。 The exhaust device for an internal combustion engine according to claim 1 or 2, wherein the control device has a larger correction amount when the hydrogen concentration in the exhaust is high than when it is low. 前記制御装置は、前記内燃機関の負荷が高いときは低いときよりも、補正量を大きくする請求項１または２に記載の内燃機関の排気装置。 The exhaust device for an internal combustion engine according to claim 1 or 2, wherein the control device has a larger correction amount when the load on the internal combustion engine is high than when the load is low. 前記制御装置は、前記内燃機関の排気の温度が低いときには高いときよりも、補正量を大きくする請求項１，２，４の何れか１項に記載の内燃機関の排気装置。 The exhaust device for an internal combustion engine according to any one of claims 1, 2 and 4, wherein the control device increases the correction amount when the exhaust temperature of the internal combustion engine is low as compared with when the temperature is high.
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